from datetime import datetime


def ndays(starttime='2021-01-18', endtime='now'):
    startdate = datetime.strptime(starttime, '%Y-%m-%d')
    if endtime == 'now':
        enddate = datetime.now()
    else:
        enddate = datetime.strptime(endtime, '%Y-%m-%d')
    return (enddate - startdate).days+1


if __name__ == '__main__':
    print(f'第{nday()}天打卡')
